BACK in college days, I held down a Saturday job at Saxone the shoe shop, whose business model seemed to be predicated on selling customers high-margin accessories of questionable value along with their footwear. Plastic shoe trees were a favourite of ours; they served no purpose but added 20 per cent to the value of a sale.

Alarmingly (for me) that was four decades ago – but the practice persists in other branches of the high street, where it’s now common custom to try to convince anyone buying a television that they need some loudspeakers to go with it.

The latest trend is for “sound bars” - rectangular strips containing a set of high, low and mid-range speakers supposedly superior to those in the TV itself. Unlike the home cinema systems that found favour in the Nineties, these are contained within a single unit and so do away with the need for 500 yards of cabling festooned across your skirting boards.

Home cinema has always been a solution in search of a problem: the sound from most TV sets is perfectly adequate, and augmentation is only really necessary if you want the kind of cavernous effects in your living room that you get at the local Odeon.

Nevertheless, as TV sets get slimmer, the space available for loudspeakers becomes ever more squeezed – and it is perhaps this realisation that now causes around a quarter of television buyers to also stump up for a sound bar on the spot.

You can pick one up for as little as £50 but the average price is closer to £200. The bar simply sits below your TV – no fixing is necessary – and when plugged in, bypasses the normal speakers. If you connect it with an optical digital (Toslink) or HDMI cable you can control the sound bar’s volume from your normal TV remote and also send it the output of your DVD. But beware of cheap sound bars that have only analogue connectors.

Any decent unit will have a deep sub-woofer speaker for booming bass, and often this is contained within a separate box. The sound from these is great when accompanying a Quentin Tarantino movie but too boxy for pleasant music reproduction.

Manufacturers rate speakers in watts but there are too many conflicting standards of measurement to make the figures meaningful. Rely on your ears instead, but bear in mind that the acoustics in a shop will be different to those in your living room. This is especially true if you’re buying a new TV; take it home first before deciding whether to spend almost as much again on something that may turn out to be as much use to you as a pair of plastic shoe trees.